To make the porcini dust: Add dried porcini mushrooms to a spice grinder. Pulse until finely ground.

Add porcini dust and salt and pepper to tray or large plate Mix to combine. Brush tenderloin with oil. Roll and coat tenderloin in porcini mixture. Transfer to large oven-proof skillet.

Roast tenderloin until meat reaches and internal temperature of 140 degrees F. for medium rare, about 20 to 25 minutes depending on thickness of meat, or until done to your liking.

Remove tenderloin from pan and let rest for 10 to 12 minutes before slicing. Keep tenderloin warm and tent with foil. Use this pan to make the sauce.

Add 1 tbsp. butter to pan over medium heat. Add shallot, stir and cook until softened, about 1 to 2 minutes. Deglaze pan with brandy, wine and stock and let reduce until syrupy, about 10 to 12 minutes. Remove from heat and swirl in 1 to 2 tbsp. butter. Season sauce with salt and pepper and finish with tarragon.